IPQoS adds the flowacct accounting module to the Diffserv model. You can use flowacct to gather statistics on traffic flows, and bill customers in agreement with their SLAs. Flow accounting is also useful for capacity planning and system monitoring.
Number of packets
Number of bytes
You can also gather statistics on other attributes, as described in Recording Information About Traffic Flows, and in the flowacct(7ipp) and acctadm(1M) man pages.
For information on planning a flow-accounting strategy, see How to Plan for Flow Accounting.